Characteristics of Nitrogen Pollution and the Potential Mineralization in Surface Sediments of Dianchi Lake

The nitrogen content,its different forms and their spatial distribution were studied by using the 53 sediment samples from different sites in Dianchi Lake. Thereafter, the potential nitrogen mineralization ability of the sediments and their pollution characteristics were also explored to understand the influencing factors of nitrogen pollution and its release risk from the sediment surface to the overlying water of Dianchi. The results showed: 1 the average total nitrogen content of surface sediment in Dianchi Lake was 3 515. 60 mg·kg- 1,which was at a high level from the inlets in Caohai Northeast thinning digging area,Panlong River and the Haikou into Dianchi Lake,but relatively low in Baoxiang River Estuary dredging area. The total organic nitrogen( TON) content,accounting for 85. 86% of TN,was at a high level; on the other hand,the dissolved inorganic nitrogen( DIN) content was lower,which accounted for 14. 10% of TN. The spatial distribution of TON and TN kept the same trend,but not the DIN. Compared with other Lakes of China,the nitrogen content of sediment in Dianci was at a high level,and the extent of pollution was just below the serious polluted City Lakes. 2 The average potential mineralizable nitrogen( PMN) content of Lake Dianchi was 1 154. 76 mg·kg- 1,accounting for 32. 90% of TN,which raised the potential risk of its release into the overlying water. Higher PMN was found in the Caohai Lake area and the inlet of Panlong River in the North,the inlet of Luolong Rive in the Middle Lake,the inlet of Baiyukou Lake and Liangwang River in the South. Nowadays,the p H value of Dianchi Lake was favorable for its sediment nitrogen mineralization,and its nitrogen mineralization was affected by the release of NH+4-N from organic matter. In the heavy polluted area,the concentration of the overlying water nitrogen was seriously affected by nitrogen mineralization of sediment from Dianchi,while the light polluted area was less affected.